Oldest Dino Embryo Boneyard Provides New Insight for Researchers

While these never actually walked the Earth, and didn´t fully develop or hatch, a trove of dinosaur embryos could give researchers rare insight into their development. Paleontologists working in China recently unearthed what could be the earliest collection of fossilized dinosaur embryos to date, and it has provided the researchers with a new opportunity to study ongoing growth patterns and development of the prehistoric species.

The bones, which were found in a 190-million-year-old dinosaur bonebed near the city of Lufeng, in Yannan China are from about 20 embryonic individuals of the long-necked sauropodomorph Lufengosaurus, which was reportedly the most common dinosaur in the region during the Early Jurassic period. A fully-grown adult Lufengosaurus measured approximately eight meters long.

This research was led by University of Toronto Mississauga paleontologist Robert Reisz, and included an international team of researchers and scientists from Canada, Taiwan, the People’s Republic of China, Australia, and Germany. The team excavated and analyzed more than 200 bones from individual dinosaurs at different stages of embryonic development.

“We are opening a new window into the lives of dinosaurs,” said Reisz. “This is the first time we’ve been able to track the growth of embryonic dinosaurs as they developed. Our findings will have a major impact on our understanding of the biology of these animals.”

The research is published in the April 11 issue of Nature.

To date, only about one square meter of the bonebed has been excavated, but researchers noted that this small area has already yielded pieces of eggshell, the oldest known for any terrestrial vertebrate. Reisz said this is the first time that even fragments of such delicate dinosaur eggshells, less than 100 microns thick, have been found in such good condition.

However, what makes this study unique is that almost all known dinosaur embryos are from the Cretaceous Period, which ended some 125 million years after the bones at the Lufeng site were buried and fossilized.

“Most of our record of dinosaur embryos is concentrated in the Late Cretaceous period,” David Evans, curator of vertebrate paleontology at the Royal Ontario Museum in Toronto told Nature. “This [study] takes a detailed record of dinosaur embryology and pushes it back over 100 million years.”

The disarticulated bones are believed to have come from several different nests containing dinosaurs at various embryonic stages. Dinosaur embryos are often found in single nests or partial nests, and thus have typically offered only a snapshot of one development stage.

This study concentrated on the largest embryonic bone, the femur, which showed a consistently rapid growth rate, doubling in length from 12 to 24 mm as the dinosaur grew within the eggs. This rapid growth could indicate that sauropodomorphs like Lufengosaurus had a short incubation period.

The team further found that the femurs were reshaped even as these developed with the egg, while examination of the bones´ anatomy and internal structure suggested that there may have been movement within the egg.

“This suggests that dinosaurs, like modern birds, moved around inside their eggs,” Reisz added. “It represents the first evidence of such movement in a dinosaur.”

Taiwanese members of the team may have also discovered organic material inside the embryonic bones, which could be collagen, a protein characteristically found in bone.

“The bones of ancient animals are transformed to rock during the fossilization process,” said Reisz. “To find remnants of proteins in the embryos is really remarkable, particularly since these specimens are over 100 million years older than other fossils containing similar organic material.”

The researchers further believe that these dinosaurs likely maintained their extreme rate of growth after hatching in an effort to evade predation by outgrowing their predators.